In our U.S. Pat. No. 4,074,511 which is incorporated herein by reference, there is disclosed a system for forming self-twist, false-twist yarn strands. It was pointed out therein that it is highly desirable to join false-twisted yarn strands at their nodes before permitting the strands to ply together because the resulting product is more stable and its characteristics are more reliably predictable.
To accomplish that goal, the system provided a rotatable guide member in the form of a yarn wheel having circularly extending guide flanges defining guide paths therebetween. At least three such flanges are provided to define separated guide paths for at least two yarns, although multiple flanges can be used for multiple yarns, the number of flanges always being one more than the number of yarns.
The inner separatory flange or flanges are interrupted at at least one location to permit the guide paths to merge so that the yarn strands therein can be brought together and joined or locked together. The joined strands then leave the yarn wheel and are permitted to self-twist, forming a plied yarn.
The locking means disclosed in that application comprises a rotating disc, the surface of which is exposed to the strands at the interruption location. The disc rotates at a relatively high speed, engaging and entangling the fibers of the yarn strands to accomplish the locking. The disc is driven by a motor carried in the rotating yard wheel. Two or more motor and disc arrangements can be provided and located such that the circumferentail distance between discs is equal to the spacing between nodes. It will be recognized that the yarn wheel rotation speed is synchronized with the longitudinal speed of the yarn so that there is substantially no longitudinal movement of the yarn relative to the guide surfaces on which they lie.
While this arrangement is quite suitable for spun yarns of carded staple fiber, its effect is somewhat reduced in the processing of bulked continuous filament yarns. This is due to the availability of many free ends of fibers to be intertwined in the spun yarn node, whereas the continuous filament yarn has no free fiber ends available for twisting together and locking the node.
There is consequently a need for other methods of node locking, that will operate on self twist yarns of either the spun staple or continuous filament variety.